An illuminating arrangement of this kind is available commercially from Carl Zeiss under the product designation "Varioskop" together with the surgical microscope OPMI CS. In this known illuminating arrangement, even narrow surgical channels can be illuminated because of the illuminating beam path running essentially coaxially to the optical axis of the surgical microscope. The diameter of the illuminated area and the illumination intensity can be varied within certain limits.
Especially in neurosurgery, it has been shown to be desirable to further increase the illumination intensity for fluorescent excitation of tumorous tissue in order to be able to do without a special fluorescence illumination such as a hand-guided light conductor wherein light emanates from the end face thereof.